The present invention relates to digital image processing.
Locating pupils in a digital image is useful in some situations. For example, flash photographs of people frequently result in a red-eye effect that can be corrected if the location of the pupil is known. The red-eye effect is a consequence of the flash illumination reflecting off of the subject's retina, returning to the camera, and appearing as a bright red dot where the pupil should be. Similar effects occur with photographs of animals, although the dot color can be different (e.g., green or yellow). Computer applications for editing images typically include tools to assist a user in correcting the red-eye effect—usually by replacing the red pupil with a more natural-looking pupil. In order to avoid requiring the user to designate precisely which pixels constitute the pupil to be corrected, such a tool can include a detector that determines the pupil position and shape to within some margin of error. In order to be sufficiently reliable, such a detector typically requires (through user action) a rough initial hint of the pupil location and size.